1. Field of the Invention
The present invention relates to a zoom lens ideal for digital still and motion cameras (DSMC), single-lens reflex cameras, and the like.
2. Description of the Related Art
Recently, in DSMCs and single-lens reflex cameras, zoom lenses are used in which a portion of the lenses in the first group are moved along the optical axis during focusing (see, for example, Japanese Patent Application Laid-Open Publication Nos. 2002-162564 and 2003-344766). Zoom lenses are also used in which a third or a fourth group configured by plural intermediate diameter lenses is moved along the optical axis during focusing (see, for example, Japanese Patent Application Laid-Open Publication No. 2010-44372).
For example, the zoom lens recited in Japanese Patent Application Laid-Open Publication No. 2002-162564 has, sequentially from an object side, a front lens component that includes plural lenses for performing zoom and focusing; and a rear lens component that includes a relay lens group having an imaging function. The rear lens component has, sequentially from the object side, a lens group A having a positive refractive power, a lens group B having a negative refractive power and movable so as to have a component in a direction orthogonal to the optical axis, and a lens group C having a positive refractive power, where the movement of the lens group B so as to have a component in a direction orthogonal to the optical axis causes displacement of the image.
The zoom lens recited in Japanese Patent Application Laid-Open Publication No. 2003-344766 includes, sequentially from the object side, a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, where the second lens group and the third lens group are moved in a direction along the optical axis to perform zooming. The first lens group is configured sequentially by a positive front group and a rear group having a stronger refractive power than the front group, where the rear group is moved in a direction along the optical axis to perform near focus and the front group is configured sequentially by a negative meniscus lens having a convex surface facing toward the object side, a positive lens whose object-side surface is convex, and a positive lens whose object-side surface is convex. The rear group is configured sequentially by a negative meniscus lens having a convex surface facing toward the object side, and a positive lens component.
The zoom lens recited in Japanese Patent Application Laid-Open Publication No. 2010-44372 has a first lens group having a positive refractive power and disposed farthest on the object side, a second lens group disposed on the image plane side of the first lens group, a Gn lens group disposed farthest on the image plane side, a Gn-1 lens group disposed on the object side of the Gn lens group, and at least 1 lens group disposed between the second lens group and the Gn-1 lens group. When zoom is performed, the first lens group and the Gn lens group are fixed. When focusing is performed, at least 1 lens group disposed between the second lens group and the Gn-1 lens group is moved and at least a portion of the Gn lens group is moved so as to have a component in a direction substantially orthogonal to the optical axis.
Nonetheless, although the anti-blur coefficient (in blur correction, the ratio of the shift amount of the image point and the shift amount of the anti-blur group) is large for the zoom lenses disclosed in Japanese Patent Application Laid-Open Publication Nos. 2002-162564 and 2003-344766, the anti-blur group is configured by 2 negative lenses and 1 positive lens and therefore, is heavy. To move the heavy anti-blur group, a strong driving power is demanded of the actuator that drives the anti-blur group. As a result, a problem arises in that the power consumption of the actuator becomes large.
Further, the zoom lens disclosed in Japanese Patent Application Laid-Open Publication No. 2010-44372 has an anti-blur group that is configured by 2 lenses and although this zoom lens having an anti-blur group configured by 2 lenses is thus, excellent on the point of the anti-blur group being light weight, since the anti-blur coefficient of the anti-blur group is small, even when a minimal image point shift is to be corrected, the anti-blur group must be shifted a lot. Consequently, the driving amount of the actuator that drives the anti-blur group becomes large and as a result, a problem arises in that the power consumption of the actuator becomes large.